Band 40, Heft 9

The new compounds LaZn 0,52 Sb 2 , LaCo 0,68 Sb 2 , LaMn x Sb 2 (0.65 ≤ x ≤ 0.76) and LaCu x Sb 2 (0.82 ≤x≤ 0.87) crystallize in the tetragonal system , space group P4/nmm (N o. 129) with the CaMnBi 2 structure. The lattice constants are: LaZn 0,52 Sb 2 : a = 438.0(3) pm, c = 1048.8(5) pm, c/a = 2.395; LaCo 0,68 Sb 2 : a = 439.4(3) pm, c = 995.4(5) pm, c/a = 2.265; LaMn x Sb 2 : für x = 0.65: a = 438.7(3) pm, c = 1078.0(5) pm, c/a = 2.457; für x = 0.76: a = 437.2(3) pm, c = 1093.3(5) pm, c/a = 2.501; LaCu x Sb 2 : für x = 0.82: a = 440.2(3) pm, c = 1015.4(5) pm, c/a = 2.307; für x = 0.87; a = 437.3(3) pm, c = 1040.0(5) pm, c/a = 2.378.

The new compounds Ca 3 GaAs 3 and Ca 3 InP 3 crystallize in the orthorhombic system, space group Pnma (No. 62) with the lattice constants Ca 3 GaAs 3 : a = 1217.1(5) pm, b = 419.7(2) pm, c = 1341.4(5) pm; Ca 3 InP 3 : a = 1201.9(5) pm, b = 413.8(2) pm, c = 1346.0(5) pm. In the structures distorted GaAs 4 - and InP 4 -tetrahedra resp. are connected by common corners to chains. The new compound Ba 3 GaSb 3 crystallizes in the orthorhom bic system, space group Pnma (No. 62) with the lattice constants a = 1411.7(5) pm, b - 2116.7(7) pm, c = 712.8(3) pm. Two distorted GaSb 4 -tetrahedra are connected by a common edge to isolated Ga 2 Sb 6 -groups. The three compounds belong to the Zintl phases.

Fe 4 S 4 I 4 2- has been prepared in tetrahydrofuran (THF) solution by the reaction of Fe, S 8 , I 2 , and Me 3 NCH 2 Ph + TI - , and isolated as black, fairly air-stable crystals of (Me 3 NCH 2 Ph) 2 Fe 4 S 4 I 4 (1) in nearly quantitative yield. 1 reacts with iron and iodine or with elemental sulfur and Fel 2 in CH 2 Cl 2 solution to form Fe 6 S 6 I 6 2- which was isolated as black crystals of (Me 3 NCH 2 Ph) 2 Fe 6 S 6 I 6 (5). In THF solution Fe 6 S 6 I 6 2- is converted to Fe 4 S 4 I 4 2- which was isolated as Fe(THF) 6 Fe 4 S 4 I 4 ·4 THF (3). Evidence is presented for an equilibrium between Fe 2 S 2 I 4 2- and Fe 4 S 4 I 4 2- , Fel 4 2- and sulfur when iron, sulfur, iodine and Et 4 N + I - react (with the required stoichiometry) to form Fe 2 S 2 I 4 2- in CH 2 Cl 2 solution. From this solution (Et 4 N) 6 (Fe 4 S 4 I 4 )2Fe 2 S 2 I 4 (6 ) crystallizes as black needles (tetragonal, P4 2 bc, a = 2467.9, b = 1653.8 pm, Z = 4). Crystals of 6 consist of the discrete anions Fe 4 S 4 I 4 2- and Fe 2 S 2 I 4 2- and Et 4 N + cations. The [Fe 4 S 4 ] 2+ core does not exhibit the usually observed core distortion. This clearly demonstrates that additional ligands (THF, CH 3 CN, iodide ions etc.) strongly reduce the stability of iodine substituted Fe/S clusters (except [Fe 4 S 4 ] 2+ cores!). The biological relevance of the observed rearrangements is discussed.

Piperidine-N-oxyboranes and 2,2,6,6-Tetramethylpiperidine-N-oxyboranes have been prepared starting from halogenoboranes by three methods: a) By reaction with N-hydroxypiperidine and triethylamine; b) by cleavage of the Si -O-bond in piperidine-N-oxy-trimethylsilanes and c) by reaction with metallated piperidine-N-oxy compounds. Diboryloxides and diborylamides, resp., are obtained upon reaction of piperidine-N-oxybrom oboranes with hexamethyldisiloxane and hexamethyldisilazane. Steric influences upon reactivity and spectroscopic properties are discussed. The compounds are characterized by elemental analysis, mass and NMR spectroscopy ( 1 H , 11 B , 13 C, 14 N, 29 Si). An X-ray analysis has been carried out for tris(2,2,6,6-tetram ethylpiperidine-1-oxy)borane 13.

The synthesis of CF 3 SCl 2 + AsF 6 - is reported. The sulfonium salt is characterised by IR, Raman, 19 F and 13 C NMR spectroscopy. The vibrational assignment is based on a C s model for the cation and assisted by a normal coordinate analysis. The crystal structure has been determined from three-dimensional diffractometer data at -133 K. The structural data for the cation are: C-F = 128.8(5) pm, C-S = 197,8(3) pm, S-Cl = 195,9(1) pm and F-C-F = 111,8(3)°, Cl-S-Cl = 104,22(5)°, C-S-Cl = 99,8(1)°.

The rubidium and ammonium thioarsenates(III) Rb 2 As 8 S 13 ·H 2 O and (NH 4 ) 2 As 8 S 13 ·H 2 O have been prepared by the reaction of the alkali carbonates with As2S3 in aqueous solution in sealed ampoules at respective temperatures of 200 °C and 220 °C. The structure of Rb 2 As 8 S 13 ·H 2 O has been established by X-ray structural analysis. The polymeric anion (As 8 S 13 2- ) n is composed of individual As 3 S 3 -rings, which are connected to one another via bridging AsS 3 -pyramids, so giving rise to infinite loop-branched dreier double chains. (NH 4 ) 2 As 8 S 13 ·H 2 O is isotypic with Rb 2 As 8 S 13 ·H 2 O.

The photo-induced reaction of CpV(CO) 4 (1) (Cp =η 5 -C 5 H 5 ) with alkynes R 1 C 2 R 2 (R 1 , R 2 = H, Me, Ph, SiMe 3 ) in pentane solution yields the substitution products CpV(CO) 2 R 1 C 2 R 2 (2). One CO ligand of complexes 2 is readily displaced by PMe 3 or t BuNC affording the derivatives CpV(CO)(L)R 1 C 2 R 2 {3(PMe 3 ), 4 ( t BuNC)}. Compounds 2-4 are characterized by their IR, 1 H, 13 C, 51 V NMR and mass spectra. The alkyne in compounds 2-4 shows typical features of a four electron ligand. The barrier for the rotation of the alkyne ligand around the vanadium alkyne bond axis in the complexes 3-4 is comparatively low (⊿ G ≠ = 44.4-68.3 kJ/mol) depending mainly on the steric requirements of the acetylene ligand.

The structure of NaRbM O3 O 10 (1) was investigated. The compound crystallizes in the space group Pnma with the lattice param eters a = 7.589 Å , b = 7.579 Å , c = 15.489 Å. Its anion chain is identical with that of Rb 2 M O3 O 10 ·H 2 O (2) but the packing is more close. Contrary to (2), (1) does not change into a monoclinic phase on heating. (2) is changed into the hydrate of (1 ) when treated with a solution of sodium chloride. The lattice parameters of several alkali trimolybdates were determined from powder patterns. The stepwise dehydration of the trimolybdate hydrates was studied by X-Ray, spectroscopical and thermoanalytical methods.

Ab initio SCF calculations at a double-ζ level were perform ed on the cations N(PH 3 ) 2 + and P(PH 3 ) 2 + . Although both structures are isoelectronic, their bonding situation is different. The latter corresponds to a dipolar structure (phosphide) with considerable negative charge at the central phosphorus atom. The d-orbitals contribute to bonding as polarization functions rather than participate in hybridization.

Sodium dialkylphosphite reacts with trichlorovinylbenzene to yield in an one-batch procedure 1-phenyl-1,2,2-ethanetrisphosphonic acid hexaalkyl esters. A carbanionic intermediate of an “anomalous Michaelis-Becker reaction” is deduced. Acidolysis of esters leads to the parent trisphosphonic acids. NMR param eters of this acid are strongly influenced by protolytic equilibrium.

The crystal and molecular structure of di-2-thienyl telluride was determined by X-ray analysis. Crystal (monoclinic) data were: a = 9.526(4), b = 6.252(4), c - 16.302(5) Å; β = 97.29(3)°, Z = 4, space group P2 1 /c. Hydrogen bonds are absent and only van der Waals forces are determining crystal packing. The C ring -Te bond distances suggest little conjugation of Te atom with the rings. Comparisons with published structures for C ar -X-C ar (X = chalcogen) type molecules revealed that the C (l)-Te-C(5) angle takes the lowest value (95.6°) in the molecule understudy. The remaining bond lengths and angles are close to standard values. The molecular conformation found in the crystal is “butterfly-like” , with thienyl ring planes nearly perpendicular to the C(l)-Te-C(5) plane and the S atoms distal to each other. Dipole moment was measured for di-2-thienyl telluride in benzene solution (μ = 1.18 D at 30°). This value, which was interpreted via classical vector addition method in terms of rotation angles about C(l)-Te and C(5)-Te bonds, showed that the molecular conformation found in the crystalline state is retained in solution.

Complexes of lithium organophosphides (CO) n M(RR′PLi) m obtained by deprotonation of the corresponding phosphine complexes (CO) n M(RR′PH) m are monodentate or bidentate ligands forming anionic binuclear complexes of the type [(M(CO) 5 ) 2 PR 2 ] - (A) or [(Mo(CO) 4 (RR'P)Mo(CO) 4 ] 2- which may be isolated as [(Ph 3 P) 2 N] + salts. Oxidation of the anions [Mo(CO) 4 (RR′P)Mo(CO) 4 ] 2- with 1 ,2-dibromoethane affords the neutral phosphido complexes (CO) 4 Mo(RR′P)Mo(CO) 4 with reactive PH functional groups. The crystal and molecular structure of [(Mo(CO) 5 ) 2 PPh 2 ] - [(Ph 3 P) 2 N] + shows a distorted tetrahedral geometry at the central P atom of the complex anion. The Mo-P bond is unusual long (2.636(1) Å), the phosphorus atom showing a pronounced trans effect on Mo-C bond lengths ((Mo-C) av trans P 1.975(5) Å, (Mo-C) av cis P 2.043(6) (Mo(1)) or 2.038(6) Å (Mo(2)), respectively).

Reactions of tin tetraacetate with various bifunctional tetradentate Schiff bases have been carried out in refluxing toluene (with the azeotropic removal of the liberated acetic acid) in 1:1 and 1:2 molar ratios. But only the diacetate derivatives of tin have been isolated as stable monomeric compounds. Benzoxazine, a potentially bifunctional tetradentate ligand, is found to undergo a rearrangement when reacted with tin tetraacetate as well as with organotin compounds. All the new compounds are characterised by NMR and IR spectral data.

σ-Crotylmetallocenyl substituted ylides (1) Cp 2 M(-CH 2 CH=CHCH 3 )(CHPPh 3 ), M=Zr,Hf, are formed upon treatment of a mixture of (s-cis-) and (s-trans-η 4 -butadiene)metallocene complexes with the phosphorus ylide methylenetriphenylphosphorane (4). From the ( s-cis-/s-trans-butadiene) zirconocene equilibrium mixture (7/5) only the (s-cis-conjugated diene)metallocene isomer reacts with the ylide at -50 °C. Under kinetic control the fram-σ-crotylzirconocenyl-ylide (lb) is formed selectively; subsequent crotyl cis-trans-isomerization (1b⇆1b′) takes place at higher temperature (> -20 °C ). A mechanism including a concerted intramolecular homo-1,5- hydrogen migration step is proposed.

The reaction of bis(2,3,4,6-tetra-0-acetyl-β-D-glucopyranosyl)disulfide with (Ph 3 P) 2 Pt(C 2 H 4 ) gives cis-di(2,3,4,6-tetra-0-acetyl-l-mercapto-β-D-glucopyranosid)bis(triphenylphosphane)platinum (II). A dithiocarbimato complex (Ph 3 P) 2 Pt(S 2 CNR) has been isolated from cis-(Ph 3 P) 2 PtCl 2 , CS 2 and 1-0-Methyl-2-amino-2-deoxy-4,6-benzyliden-α,β-D-glucopyranoside. Metal complexes with metal-carbon bonds have been prepared by oxidative addition of monosaccharide halides to (Ph 3 P) 2 Pt(C 2 H 4 ) or to cobalt(I) cobaloxime, respectively. From the reaction of (Ph 3 P) 2 Pt(C 2 H 4 ) with 2,3,4,6 -Tetra-O-acetyl-α-D-glucopyranosyl-bromide the anomers trans-(α- and β-glucopyranosyl) Pt(PPh 3 ) 2 Br have been obtained. This indicates a radical reaction.

Decacarbonyl-dirhenium(O) (1) photochemically cleaves C-H-bonds in 1,3,5-cycloheptatriene (2 ) and forms two isomeric Re 2 (CO) 8 (μ-H)(μ-η 2:1 -cycloheptatrienyl) complexes (3, 4). In addition Re(CO) 3 (η 5 -cycloheptatrienyl) (5) and Re(CO) 3 (η 5 -cycloheptadienyl) (6) are obtained. The complexes 3 and 4 show temperature dependent 1 H NMR spectra due to hindered ligand movements of the cycloheptatrienyl bridges with activation barriers of ⊿G ≠ 207 = 39.9±2 kJ mol -1 and ⊿G ≠ 255 = 48.0±2 kJ mol -1 . 3 and 4 achieve in a thermal reaction an equilibrium with populations of 0.03 and 0.97 at 350 K with ⊿G ≠ 350 - 96.5±5 kJ mol -1 . The molecular structure of the more stable isomer, Re 2 (CO) 8 (μ-H)(μ-η 2:1 -1 ,3,5-cycloheptatrien-2-yl) (4 ) was determined by X-ray structure analysis.

Azomethines, azines, vinylenes and hexatrienes containing thiophene and thieno[3,2-b]- thiophene systems have been synthesized and characterisized by their IR and 1 H NMR spectra. The liquid crystalline properties of these compounds have been studied thermically and optically by their textures and are compared with the analogous compounds having benzene rings.

The He (I) photoelectron (PE) spectra of the following methoxy (-MeO) and nitro (-NO 2 ) thiophenes: 2-MeO, 3-MeO, 2,5-di-MeO, 2-NO 2 , 3-NO 2 , 2,4 -di-NO 2 and 2,5 -di-NO 2 have been recorded and their electronic structure is discussed in terms of inductive and mesomeric effects of substituent on the electronic energy levels of thiophene.

Duricaulic acid (1), a new nitrogen containing metabolite was isolated from Aspergillus duricaulis and its structure established. 1 H and 13 C NMR of some phthalimidines are discussed.

Five biosynthetically related bufadienolides were isolated from Kalanchoe daigremontiana Hamet et Perr. and structurally elucidated by X-Ray and NMR techniques. Two compounds were orthoacetates which showed strong CNS activity.